November 12, 2002
Purdue experts caution horse owners about cornWEST LAFAYETTE, Ind. This year's corn crop is one of the worst in years, and it's harboring a toxin that is potentially fatal to some animals, according to one Purdue University expert.
"The quality of the ears is the poorest that I have seen in years," said Charles Woloshuk, an Extension specialist in mycotoxins. "Many of the samples contained small ears with less than 300 kernels per ear. There were also many barren ears. However, the major concern in Indiana will be from fumonisins."
Fumonisins are mycotoxins produced by the fungus Fusarium verticillioides. They can be toxic to horses and pigs and have been linked to health problems in humans, Woloshuk said.
Woloshuk conducts an annual survey of Indiana cornfields to determine the extent of preharvest ear rots and mycotoxins. He said fumonisins have been in a five-year decline, but this year they appeared in 13 of the samples he sent to the Animal Disease Diagnostic Laboratory.
Nine of the samples had fumonisin levels of 1.6 parts per million or less. Four others contained more disconcerting levels. Those levels ranged from 4.2 ppm to 21 ppm. According to the U.S. Food and Drug Administration, horse feed should contain less than 1 ppm of fumonisin and swine feed should have less than 10 ppm.
The FDA set thresholds because fumonisins can cause leukoencephalomalacia in horses, donkeys and mules, and pulmonary edema in swine. Woloshuk said there also is evidence that links fumonisin to cancer and fetal neural tube defects in humans.
Mark Russell, an Extension horse specialist, said leukoencephalomalacia is usually fatal because it causes brain lesions that turn the brain to mush. Symptoms can include, but aren't limited to, loss of motor control, stumbling, circling, head pressing and seizures. Russell said it would be easy to confuse fumonisin poisoning symptoms with those of West Nile virus or Equine Protazoal Myelitis (EPM).
Because of the risk to horses Woloshuk is urging caution.
"We recommend that horse owners limit the amount of corn in their feed or have their feed tested for fumonisin," he said.
He added that removing fumonisins from contaminated corn is not really possible, but cleaning, especially after drying and before delivery and storage, should remove the damaged kernels and chips that contain most of the mycotoxin.
Woloshuk said that proper storage of this year's corn crop is crucial. Nearly one-third of the ears he examined had insect damage and a striking amount of channeling, a form of insect damage. He recommends that producers dry their grain to less than 14 percent moisture and cool it to below 50 degrees Fahrenheit as soon as possible.
"Drying the grain to 15 percent moisture will stop further growth of the molds that produce aflatoxin, zearalenone, deoxynivalenol and fumonisin," he said. "However, the widespread insect damage will result in a lot of broken kernels and small corn particles in the stored grain. Storage molds, such as Aspergillus glaucus which can grow at 14 to 15 percent moisture, will find it easy to invade the kernels and cause further spoilage.
"No corn with a lot of damage should be held into next summer."
Woloshuk blamed heat, drought and insect damage for the increase in fumonisin levels. He said those factors stressed the corn crop, and the conditions were ideal for the growth of the mold that produces fumonisins.
In this year's survey Woloshuk examined corn from approximately 160 fields throughout Indiana. He examined 1,530 individual ears from 306 samples. He tests ears for mycotoxins if the severity of disease in a five-ear sample is 10 percent or greater. Of the 306 samples he examined, 29 have been sent in for mycotoxin tests.
Fifteen of those samples had no mycotoxins. One ear, with severe Gibberella ear rot, contained 40 ppm deoxynivalenal (vomitoxin) and 1 ppm zearalenone. The remaining 13 contained fumonisin.
Writer: Kay Hostetler, (765) 494-6682, email@example.com
Sources: Charles Woloshuk, (765) 494-3450, firstname.lastname@example.org
Mark Russell, (765) 494-7677, email@example.com
Purdue News Service: (765) 494-2096; firstname.lastname@example.org